As researchers continue to examine the growing number of charter schools in the United States, they have focused attention on the significant heterogeneity of charter effects on student achievement. Our article contributes to this agenda by examining the achievement effects of virtual charter schools vis-à-vis brick-and-mortar charters and traditional public schools and whether characteristics of teachers and classrooms explain the observed impacts. We found that students who switched to virtual charter schools experienced large, negative effects on mathematics and English/language arts achievement that persisted over time and that these effects could not be explained by observed teacher or classroom characteristics.